American scientists use CRISPR to modify human embryos

Zayani Bhatt, 31 Jul 2017

Dr Shoukhrat Mitalipov of Oregon Health and Science University led the research that edited the DNA of viable human embryos. Photo credit: Daniel Berman/Stat News

For the first time, scientists from the Oregon Health and Science University in the United States have successfully created genetically modified human embryos. Led by embryologist, Dr Shoukhrat Mitalipov – a researcher at the university – the team used the gene-editing technique CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) to introduce gene-editing chemicals to single-cell embryos.

The aim of the experiment was to target a gene associated with a significant human disease and see if the gene was modified.

“This is the kind of research that is essential if we are to know if it’s possible to safely and precisely make corrections in embryos’ DNA to repair disease-causing genes,” shares Alta Charo, a legal scholar and bioethicist at the University of Wisconsin.

Thus far, such experiments have only been conducted in China – as scientists, religious organisations, civil society groups and even many biotechnology companies in America have been vehemently opposed to them.

However, the team was able to move forward with their experiment because of a report by the US National Academy of Sciences in February this year. The report agreed to laboratory research on germline modification as it argued, may one day be a way for parents with severe genetic disorders to have healthy, biological children.

“But we anticipated that there would need to be a lot of research to see if you could make these changes without any unintentional effects,” remarks Charo, who co-chaired the Academies committee.

It seems Mitalipov was able to do just that

In their experiment, Mitalipov and his team’s experiment were able to go further than those conducted in China – both in the number of embryos experimented on, and by showing that it is possible to safely and efficiently rectify flawed genes. Many tens of embryos were created for the experiment using sperm donated by men carrying inherited disease mutations.

The team chose to inject the CRISPR into eggs at the same time as they were fertilised by sperm. It was conducted in this way in order to avoid the pitfalls faced by the Chinese researchers. One pitfall was mosaicism, in which the desired DNA changes are taken up by only some of the cells in the embryo, not all; and the second are ‘off-target’ effects, in which genes that were not meant to be edited, are.

“It is proof of principle that it can work. They have significantly reduced mosaicism. I don’t think it’s the start of clinical trials yet, but it does take it further than anyone has before,” comments a scientist familiar with the project.

This is important as much of the criticism against germline engineering has been the concern that errors such as mosaicism and off-target editing make CRISPR an unsafe way to create human beings.

Although none of the embryos were permitted to develop for more than a few days and the team had no intention of implanting the embryos into a womb – news of the experiment has brought to the forefront again, conversation around ‘designer babies’. An example situation would be in China, where more and more parents are opting for genetic testing in order to uncover their child’s talents.

Fears over the potential beyond imagining

Able to engineer genetic enhancements, such as greater intelligence or improved athletic ability, the United States intelligence called CRISPR a potential “weapon of mass destruction” last year.

“Genome editing to enhance traits or abilities beyond ordinary health, raises concerns about whether the benefits can outweigh the risks, and about fairness if available only to some people,” explains Charo.

Additionally, because changes that are made to the embryo’s cells will also be found in the eggs or sperm that will be produced if the embryo is allowed to develop into an adult human, any children the person has will also inherit the changes.

This ability to change human evolution has triggered fears. However, Stanford University law professor and bioethicist Hank Greely responds that “the key point” is that the team did not implant any edited embryos. He argues that “research embryos” that are “not to be transferred for possible implantation” are “not a big deal”.

In America, parliamentary government has prohibited using edited IVF embryos to make people and the Department of Health and Human Services has forbidden the technology to do so from reaching clinical trials.

“While there will be time for the public to decide if they want to get rid of regulatory obstacles to these studies, I do not find them inherently unethical,” expresses Charo.

Indeed, for now, small, correctly-performed experiments such as Mitalipov’s does beg the question: whether Charlie’s Gard’s situation would have been different had his parents had access to CRISPR technology. MIMS

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